Ion implantation method and ion implantation apparatus

ABSTRACT

In an ion implantation method, ion implantation into a substrate is performed while changing a relative positional relation between an ion beam and the substrate. A first ion implantation process in which a uniform dose amount distribution is formed within the substrate and a second ion implantation process in which a non-uniform dose amount distribution is formed within the substrate are performed in a predetermined order. Moreover, a cross-sectional size of an ion beam irradiated on the substrate during the second ion implantation process is set smaller than a cross-sectional size of an ion beam irradiated on the substrate during the first ion implantation process.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a divisional application of U.S. application Ser. No. 13/053,624filed Mar. 22, 2011, which claims priority from Japanese PatentApplication No. 2011-020362, filed on Feb. 2, 2011. The entiredisclosure of U.S. application Ser. No. 13/053,624 and Japanese PatentApplication No. 2011-020362 are each incorporated herein in entirety byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an ion implantation method and an ionimplantation apparatus capable of forming a non-uniform distribution ofa dose amount within a substrate.

2. Description of the Related Art

Ion implantation process is one of the manufacturing processes of asemiconductor substrate. In the ion implantation process, ionimplantation is sometimes performed such that a distribution of an ionimplantation amount (also referred to as a dose amount) that isimplanted within a substrate (for example, a wafer or a glass substrate)is non-uniform.

For example, in the manufacturing process of the semiconductorsubstrate, there is a problem that characteristics of a semiconductordevice that is manufactured on a one substrate become non-uniform withinthe substrate.

To compensate for such a non-uniform distribution of the characteristicsof the semiconductor device, conventionally, a method is used by which adose amount implanted within the substrate in the ion implantationprocess is non-uniformly distributed within the substrate.

A concrete method is disclosed in Patent Document 1. Patent Document 1discloses an ion implantation apparatus that realizes implantation ofions into the substrate by reciprocally driving the substrate in a Ydirection, and scanning a spot-like ion beam in an X direction that isorthogonal to the Y direction by virtue of an electric field or amagnetic field. Such an ion implantation apparatus is called a hybridscanning system. With such an ion implantation apparatus, a non-uniformdose amount distribution can be formed within the substrate by changinga scanning speed of the ion beam depending on a position of the ion beamon the substrate.

Moreover, in the manufacturing process of the semiconductor substrate,to improve a utilization efficiency of the substrate, a technique hasbeen used from the past in which a semiconductor device having differentcharacteristics is manufactured in different regions on a singlesubstrate. An example of such a technique is disclosed in PatentDocument 2.

In Patent Document 2, ion implantation into the substrate is performedusing the ion implantation apparatus of the hybrid scanning systemsimilar to Patent Document 1. First, to form distribution of twodifferent dose amounts on either side of a center portion of thesubstrate, ion implantation into the substrate is performed by changingeither the scanning speed of the ion beam or a driving speed of thesubstrate to a different value when the ion beam crosses the centerportion of the substrate. Subsequently, the substrate is rotated by 90degrees and the ion implantation is performed by changing either thescanning speed of the ion beam or the driving speed of the substrate toa different value when the ion beam again crosses the center portion ofthe substrate. In this manner, four regions having different dose amountdistributions are formed in the substrate.

Patent Document 1: Japanese Patent Application Laid-open No. 2010-118235(FIGS. 3 to 10 and FIGS. 12 to 18) Patent Document 2: Japanese PatentApplication Laid-open No. 2003-132835 (FIGS. 1 to 10, Paragraphs 0062 to0064, and 0096).

As described in Paragraphs 0062 to 0064 and 0096 of Patent Document 2,changing the scanning speed of the ion beam or the driving speed of thesubstrate to a desired value takes time; however, short. If the ion beamis irradiated on the substrate while the speed is being changed to thedesired speed, a region of an undesired dose amount distribution calleda transition region is formed in the substrate.

FIG. 11 depicts states of the transition region. (A) depicts an intendeddose amount distribution to be formed beneath the surface of thesubstrate. In (A), a concentric dose amount distribution is explained asan example. It is an objective to form a region of a dose amount D2 at acentral region and a region of a dose amount D1 at an outercircumferential region. (B) depicts a state of the dose amountdistribution when the substrate is cut along a line A-A shown in (A). Anaxis of abscissa shown in each of the graphs (B) to (E) of FIG. 11indicates a position on the line A-A. The line A-A shown in FIG. 11 at(A) and (F) passes through a center of the substrate and divides thesubstrate into two portions.

In this example, for the sake of simplicity, a current density of theion beam and the driving speed of the substrate are always assumed to beconstant in the ion implantation apparatus of the hybrid scanningsystem. In this case, the dose amount implanted into the substrate isinversely proportional to the scanning speed of the ion beam. Therefore,to obtain the dose amount distribution shown in (B), it is necessary tochange the scanning speed of the ion beam in the manner shown in (C).

However, because some time is required for changing the scanning speed,the scanning speed of the ion beam is actually changed in the mannershown in (D). As a result, the dose amount distribution shown in (E) isformed on the line A-A. In the dose amount distribution finally formedwithin the substrate, a transition region R is formed in a region otherthan the regions of the dose amounts D1 and D2 shown in (F).

A larger transition region leads to insufficient compensation of thecharacteristics distribution of the semiconductor device. Thus, it isdesirable that the transition region be as small as possible. In PatentDocument 2, a technique of reducing a size of the ion beam is proposedfor making the transition region smaller. Concretely, to change thescanning speed of the ion beam scanned in the X direction at the centerportion of the substrate, Wx that is a size of the ion beam in the Xdirection, is reduced. When the size of the ion beam is reduced, a beamcurrent reduces by an equivalent amount. Therefore, if the ionimplantation process to the substrate is performed using such an ionbeam, a longer time is required for achieving a desired dose amountdistribution. To solve this problem, a method is proposed in which Wythat is a size of the ion beam in the Y direction, which is orthogonalto the X direction, is increased and reduction of the beam current ofthe ion beam is restrained by performing the ion implantation processusing the ion beam that is roughly elliptical.

However, even if an elliptical ion beam proposed in Patent Document 2 isused for forming a circular dose amount distribution on the substrate asmentioned in Patent Document 1 or shown in FIG. 11, the time required toperform the ion implantation process cannot be shortened while reducingthe transition region and restraining reduction in the beam current.

In the circular dose amount distribution mentioned in Patent Document 1or shown in FIG. 11, the dose amount distribution changes in the Ydirection when the ion beam is scanned on the substrate in the Xdirection. As a result, because it is necessary to make the transitionregion smaller even in the Y direction, it is not sufficient to use onlythe elliptical ion beam as proposed in Patent Document 2.

SUMMARY OF THE INVENTION

The present invention has been achieved to solve at least the aboveproblems. An object of the present invention is to provide an ionimplantation method and an ion implantation apparatus by which a smallertransition region with an undesired dose amount distribution can beobtained as well as the time required for an ion implantation processcan be shortened regardless of a shape of a non-uniform dose amountdistribution formed beneath a surface of a substrate.

In an ion implantation method according one aspect of the presentinvention in which ion implantation to the substrate is performed whilechanging a relative positional relation between the ion beam and thesubstrate, a first ion implantation process by which a uniform doseamount distribution is formed within the substrate, and a second ionimplantation process by which a non-uniform dose amount distribution isformed within the substrate are performed in a predetermined order.Furthermore, a crosssectional size of the ion beam that is irradiated onthe substrate during the second ion implantation process is set smallerthan a cross-sectional size of the ion beam that is irradiated on thesubstrate during the first ion implantation process.

Thus, because the non-uniform dose amount distribution is formed withinthe substrate by combining the ion implantation process that uses theion beam having a larger cross-sectional size and the ion implantationprocess that uses the ion beam having a smaller crosssectional size, notonly the transition region formed on the substrate can be madesufficiently small, but also the time required for the ion implantationprocess can be shortened.

When processing a plurality of substrates using the first and second ionimplantation processes, it is desirable to successively perform one ofthe ion implantation processes on the substrates, and thereafter, theother ion implantation process is successively performed on thesubstrates.

When the structure described above is used, when changing operatingparameters of the ion implantation apparatus for the first and secondion implantation processes, the operating parameters can be changed atone time. Thus, because there is no need to take into consideration awaiting time until the ion implantation apparatus is re-operated due tochange in the operating parameters, the time for completing the ionimplantation process can be shortened by an equivalent time.

An ion implantation apparatus, which performs ion implantation into asubstrate while changing a relative positional relation between the ionbeam and the substrate, includes a control device including a functionthat exerts control to perform a first ion implantation process in whicha uniform dose amount distribution is formed within the substrate and asecond ion implantation process in which a non-uniform dose amountdistribution is formed within the substrate in a predetermined order,and sets a cross-sectional size of an ion beam that is irradiated on thesubstrate during the second ion implantation process smaller than across-sectional size of an ion beam that is irradiated on the substrateduring the first ion implantation process.

When processing a plurality of the substrates using the first and secondion implantation processes, it is desirable that the control deviceincludes a function that exerts control to select and successivelyperform one of the ion implantation processes on the substrates, andthereafter, successively perform the other ion implantation process onthe substrates.

If the ion implantation apparatus is structured as described above,advantages similar to the ion implantation method described above can beobtained.

Furthermore, a structure of the ion implantation apparatus describedbelow can be adopted. That is, the ion implantation apparatus mayinclude a beam shaping mask that shapes the ion beam irradiated on thesubstrate. It is desirable that the control device includes a functionthat adjusts a position of the beam shaping mask depending on which oneof the first and second ion implantation processes is to be performed.

If the beam shaping mask is used as described above, the cross-sectionalsize of the ion beam can be easily adjusted.

According to the present invention, a transition region having anundesired dose amount distribution can be made smaller and the timerequired to perform the ion implantation process can be shortenedregardless of a shape of a non-uniform dose amount distribution formedwithin the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a plan view that depicts an example of an ion implantationapparatus according to the present invention;

FIG. 2 is a flowchart of an example of a nonuniform implantation processaccording to the present invention;

FIGS. 3A to 3D are drawings that depict a relation of cross-sectionalsizes of an ion beam that is irradiated on a substrate in a first ionimplantation process and a second ion implantation process of thepresent invention;

FIG. 4 is a flowchart of another example of a non-uniform implantationprocess according to the present invention that continues to A in FIG.5;

FIG. 5 is the flowchart of the other example of the non-uniformimplantation process according to the present invention, that iscontinued from A shown in FIG. 4.

FIG. 6 is a drawing that depicts an example of a non-uniform dose amountdistribution formed beneath a surface of the substrate using the firstand second ion implantation processes of the present invention;

FIG. 7 is a drawing that depicts another example of the non-uniform doseamount distribution formed within the substrate using the first andsecond ion implantation processes of the present invention;

FIG. 8 is a drawing that depicts an example of an acceleration tubeincluded in the ion implantation apparatus shown in FIG. 1 of thepresent invention;

FIG. 9 is a drawing that depicts an example of a quadrupole lensincluded in the ion implantation apparatus shown in FIG. 1 of thepresent invention;

FIGS. 10A to 10C are drawings that depict examples of a beam shapingmask included in the ion implantation apparatus shown in FIG. 1 of thepresent invention; and

FIG. 11 depicts how a transition region is formed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Exemplary embodiments of an ion implantation method and an ionimplantation apparatus according to the present invention are explainedbelow with reference to the accompanying drawings. Directions of X, Y,and Z axes shown in the accompanying drawings are orthogonal to eachother. The Z direction indicates a traveling direction of an ion beamand the X direction indicates a scanning direction of the ion beam.

FIG. 1 is a drawing that depicts an example of an ion implantationapparatus 1 according to the present invention. The X, Y, and Z axesshown in FIG. 1 indicate directions inside a processing chamber 14 thatis described later. The ion implantation apparatus 1 is an ionimplantation apparatus of a so-called hybrid scanning system, andincludes functions that are equivalent to those of ion implantationapparatuses disclosed in Patent Documents 1 and 2.

A structure of each unit is briefly explained below. A spot-like ionbeam 3 emitted from an ion source 2 is deflected by a mass analysismagnet 4 and ions of only desired components are extracted from the ionbeam 3 at an analysis slit (not shown). Thereafter, the ion beam 3passes through an acceleration tube 5, and is converted into the ionbeam 3 having desired energy.

After passing through the acceleration tube 5, the ion beam 3 is shapedby a quadrupole lens 6 and incident on an energy separator 7. The energyseparator 7 is made of an electromagnet in the same manner as the massanalysis magnet 4. The energy separator 7 deflects the ion beam 3 by apredetermined deflection amount and separates neutral particles orunnecessary energy components from the ion beam 3.

A scanner 8 scans the ion beam 3 by virtue of a magnetic field or anelectric field in the X direction such that the ion beam 3 wider than awidth of a substrate 11 in the X direction.

The ion beam 3 that is scanned by the scanner 8 is deflected by acollimator magnet 9 such that an outer shape of the ion beam 3 isparallel to the Z direction. Thereafter, the ion beam 3 passes through abeam shaping mask 10, and is irradiated on the substrate 11 placedinside the processing chamber 14.

The substrate 11 is held on a platen 12 by electrostatic adsorption, andthe platen 12 is coupled to a scanning shaft (not shown) that extendsalong the Y direction. A motor is provided in a driving device 13. Themotor causes reciprocal driving of the scanning shaft along the Ydirection, thus causing the ion beam 3 to be irradiated on the entiresurface of the substrate 11.

A control device 30 is provided in the ion implantation apparatus 1. Thecontrol device 30 includes a function that controls various power supplyunits. To adjust a cross-sectional size of the ion beam 3 that isirradiated on the substrate 11, the control device 30 exchanges electricsignals (S), in a wired or wireless manner, between the power supplyunits included in each of the driving devices of, for example, the ionsource 2, the acceleration tube 5, the quadrupole lens 6, and the beamshaping mask 10. The power supply units described above are controlledby the control device 30 by way of switching between a first ionimplantation process and a second ion implantation process that aredescribed later.

Apart from the function described above, the control device 30 can alsoinclude a function that controls the scanning speed of the ion beam 3scanned by the scanner 8 and a driving speed at which the substrate 11is driven, or a function that controls other optical elements (massanalysis magnet 4, energy separator 7, etc.). Furthermore, the controldevice 30 can also include a function that places the substrate 11,which is transported in the processing chamber 14 by a transportmechanism (not shown), at a predetermined implantation position, or afunction that removes the substrate 11 from the implantation positionand transports it to the outside of the processing chamber 14. A secondcontrol device can be provided in the ion implantation apparatus 1 and afunction that controls the scanner 8, etc., described above can beprovided in the second control device. When the second control device isprovided, an arrangement is made such that electric signals can becommunicated between the two control devices and a relation isestablished such that one control device can control the other controldevice.

As disclosed in Patent Document 2, if the object is to make a transitionregion smaller, then it is sufficient to reduce a size of the ion beam 3that is irradiated on the substrate 11. However, when the size of theion beam 3 is reduced without changing current density of the ion beam3, more time is required to form a desired non-uniform dose amountdistribution within the substrate 11. On the other hand, when the sizeof the ion beam 3 is increased without changing current density of theion beam 3, the desired non-uniform dose amount distribution within thesubstrate 11 can be achieved in a shorter time; however, the transitionregion becomes larger.

Considering the points described above, ion implantation processes oftwo types are performed in the present invention using ion beams ofdifferent crosssectional sizes that are irradiated on the substrate.FIG. 2 is a flowchart explaining an example of a non-uniformimplantation process according to the present invention. The non-uniformimplantation process is explained in detail below.

In the flowchart shown in FIG. 2, a process is explained in which asubstrate is arranged one by one at an implantation position, and thefirst and second ion implantation processes are successively performed(S101-S105). More specifically, at S101, the number of substrates to beprocessed is decided in the non-uniform implantation process. M units ofsubstrates are processed, and at S102, N is set to be equal to 1. AtS103, the N-th substrate is arranged at an implantation position.Further, at S104, a first ion implantation process is performed,followed by a second ion implantation process at S105. Thereafter, theprocessed substrate is removed from the implantation position (S106),and it is determined whether the counter N has reached a value of MatS107. If no, then the counter is increased by N=N+1 at S108, and theseries of processes is repeated until all the substrates areprocessed(S103-S108).

In the first ion implantation process, a uniform ion implantationprocess is performed within the substrate 11 using an ion beam of alarge cross-sectional size. Subsequently, in the second ion implantationprocess, a non-uniform ion implantation process is performed within thesubstrate 11 using an ion beam of a smaller crosssectional size than theion beam used in the first ion implantation process. The dose amountdistribution finally formed within the substrate is a combination of thedose amount distributions formed by the first and second ionimplantation processes. The term “uniform” implies that the value of thedose amount is substantially constant within the entire substrate andthe term “non-uniform” implies that the value of the dose amount is notconstant within the entire substrate.

By combining the dose amount distributions formed by the different ionimplantation processes, the transition region can be made smaller andthe desired non-uniform dose amount distribution can be formed withinthe substrate 11 in a shorter time. The example in which the second ionimplantation process is performed subsequent to the first ionimplantation process is explained here; however, this sequence can bereversed. That is, the first ion implantation process can be performedsubsequent to the second ion implantation process.

FIGS. 3A to 3D are drawings that depict examples that show a relation ofcross-sectional sizes of the ion beam that is irradiated on thesubstrate in the first and second ion implantation processes. FIG. 3A isa drawing that depicts a cross-sectional shape of the ion beam 3 used inthe first ion implantation process. In FIGS. 3B to 3D, an outline of theion beam 3 used in the first ion implantation process is shown by adashed line. A solid line shown in FIGS. 3B to 3D depicts across-sectional shape of the ion beam 3 used in the second ionimplantation process.

In the present invention, the cross-sectional size of the ion beam 3used in the second ion implantation process is smaller than thecross-sectional size of the ion beam 3 used in the first ionimplantation process. A magnitude relation of the cross-sectional sizesis as follows. When the cross-sectional shape of the ion beam 3irradiated on the substrate 11 is considered, the crosssectional shapeof the ion beam 3 used in the second ion implantation process fallswithin the cross-sectional shape of the ion beam 3 used in the first ionimplantation process. In this manner, the cross-sectional size of theion beam 3 used in the second ion implantation process is smaller thanthe cross-sectional size of the ion beam 3 used in the first ionimplantation process.

More specifically, as shown in FIGS. 3B to 3D, the cross-sectional shape(dashed line) of the ion beam used in the first ion implantation processencloses the cross-sectional shape (solid line) of the ion beam used inthe second ion implantation process.

FIGS. 4 and 5 are flowcharts explaining another example of thenon-uniform implantation process according to the present invention. Theexample shown in FIGS. 4 and 5 differs from the example shown in FIG. 2in that the first ion implantation process is successively performed ona plurality of the substrates (S201-S207), More specifically, at S201,the number of substrates to be processed is decided in the non-uniformimplantation process. M units of substrates are processed, and at S202,N is set to be equal to 1. At S203, the N-th substrate is arranged at animplantation position. Further, at S204, a first ion implantationprocess is performed. Thereafter, the processed substrate is removedfrom the implantation position at S205, and it is determined whether thecounter N has reached a value of M at S206. If no, then the counter isincreased by N=N+1 at S207, and the series of processes is repeateduntil all the substrates are processed. And thereafter, the second ionimplantation process is successively performed on the substrates(S208-S213). More specifically, at 208, N is set to be equal to 1. AtS209, the N-th substrate is arranged at an implantation position.Further, at S210, a second ion implantation process is performed.Thereafter, the processed substrate is removed from the implantationposition at S211, and it is determined whether the counter N has reacheda value of M at S212. If no, then the counter is increased by N=N+1 atS213, and the series of processes is repeated until all the substratesare processed. Similar to the example given in FIG. 2, the order ofexecution of the first ion implantation process and the second ionimplantation process can be reversed.

In the ion implantation process, operating parameters of the ion source2 and various magnets of the ion implantation apparatus 1 are changedwhen the crosssectional size of the ion beam 3 changes. For example, inthe example shown in FIG. 2, the operating parameters should be changedat least between each implantation process every time a substrate isprocessed. Extra time is required when processes such as checkingwhether the ion beam 3 having the desired cross-sectional size isirradiated on the substrate 11 and correcting values of the operatingparameters if the ion beam 3 does not have the desired cross-sectionalsize are performed after the operating parameters are changed.

In view of this fact, as shown in FIGS. 4 and 5, shortening of the timerequired for the ion implantation process can be anticipated bysuccessively performing each ion implantation process for a plurality ofthe substrates. Here, a plurality of the substrates implies, forexample, substrates in a lot.

FIG. 6 is a drawing that depicts an example of a non-uniform dose amountdistribution formed within the substrate 11 using the first and secondion implantation processes of the present invention. Regions with highdose amounts forming a substantially ring shape are formed in a portionof the substrate 11.

For example, uniform ion implantation of a dose amount Do is performedwithin the entire substrate 11 by the first ion implantation process.Thereafter, the scanning speed of the ion beam 3 and the driving speedof the substrate 11 are controlled according to the position of the ionbeam 3 on the substrate 11 so as to implant a dose amount 0 10 or a doseamount 0 20 in predetermined regions.

FIG. 7 is a drawing that depicts a state in which regions of differentdose amounts are divided into two regions at a center portion of thesubstrate 11. Although the dose amount distribution is formed as shownin FIG. 7, the non-uniform dose amount distribution including a smalltransition region can be formed within the substrate 11 within a shortertime by performing the two ion implantation processes similar to the ionimplantation processes performed for the dose amount distribution shownin FIG. 6.

How much dose amount is to be implanted in the first and second ionimplantation processes when implanting the ions to the substrate 11 isdetermined in the manner as explained below.

In FIGS. 6 and 7, focus is trained on the dose amount implanted in thesecond ion implantation process. What will be the percentage of a highdose amount portion (dose amount D20) relative to a low dose amountportion (dose amount D10) (called dose ratio and expressed by X inEquation 1) is expressed by the following Equation 1:X=(D ₂₀ /D ₁₀)−1  (1)

Equation 1 can be modified to Equation 2:X=(D ₂ −D ₀ /D ₁ −D ₀)−1  (2)

Equation 2 can be further modified to Equation 3:D ₀=(1/X)(D ₁ −D ₂)+D ₁  (3)

The dose ratio X is used to determine how much transition region isallowable when the characteristics of a semiconductor device arecompensated, or to determine a range of a value that is allowable basedon conditions of response characteristics, etc. when changing thescanning speed of the ion beam 3 or the driving speed of the substrate11 included in the ion implantation apparatus 1.

It is desirable to select a value that is a maximum nearest value withinthe allowable range as the dose ratio X for shortening the time requiredfor the ion implantation processes. This is because, as the dose ratio Xincreases, a large amount of ion implantation is performed by the firstion implantation process. When performing implantation of the same doseamount without changing current density of the ion beam 3, between thefirst ion implantation process using the ion beam 3 of the largecross-sectional size and the second ion implantation process using theion beam 3 of the small cross-sectional size, the time required forimplantation performed using the first ion implantation process isshorter. Thus, to shorten the time required for the entire implantationprocess, it is desirable to perform ion implantation by the first ionimplantation process for as long as possible.

Considering the points described above, if an optimum value of the doseratio X is determined, because the dose amounts D1 and D2 are knownvalues determined based on the desired non-uniform dose amountdistribution, a value of the dose amount Do that should be implanted bythe first ion implantation process can be determined. The first ionimplantation process is performed using the determined dose amount D₀.

Various methods could be considered for adjusting the cross-sectionalsize of the ion beam. Some concrete examples are explained below.

FIG. 8 is a drawing that depicts an example of the acceleration tube 5included in the ion implantation apparatus 1 shown in FIG. 1. Theacceleration tube 5 includes, in the Z direction, three tubularelectrodes of different electric potentials, namely, a high-voltage sideelectrode 16, a focusing electrode 18, and an earth-side electrode 17.An insulating glass 15 is arranged between the electrodes. Anacceleration-deceleration power supply unit 19 is connected between thehigh-voltage side electrode 16 and the earth-side electrode 17. Theenergy of the ion beam 3 that passes through the acceleration tube 5 isadjusted by adjusting the acceleration-deceleration power supply unit19. Furthermore, a focusing power supply unit 20 is connected betweenthe high-voltage side electrode 16 and the focusing electrode 18. In theacceleration tube 5, a desired electric field is generated between theelectrodes by adjusting the focusing power supply unit 20, and anarrangement is made such that the ion beam 3 that passes through thegenerated electric field converges or diverges. The cross-sectional sizeof the ion beam can be suitably adjusted in the first and second ionimplantation processes using the acceleration tube 5 having thestructure described above.

FIG. 9 is a drawing that depicts an example of the quadrupole lens 6included in the ion implantation apparatus 1 shown in FIG. 1. Thequadrupole lens 6 that uses an electromagnet is explained as an example.The quadrupole lens 6 has four magnetic poles 27 and a coil 28 is woundaround each of the magnetic poles 27. An electric current I is suppliedto each coil 28 and four polarities are formed at a tip of the magneticpoles 27. A magnetic field B is generated between the tips of themagnetic poles 27. A Lorentz force F is generated in the ion beam 3 thatpasses through the magnetic field B. In the example shown in FIG. 9, theion beam 3 is shaped by the Lorentz force F such that it becomes shorteralong the X direction and longer along the Y direction. Specifically,the shape of the ion beam 3 shown by the solid line in FIG. 9 istransformed to an elliptical shape as shown by the dashed line. The sizeof the ion beam 3 is reduced by removing a portion in a longitudinaldirection of the ion beam 3 that is formed in the elliptical shape bythe quadrupole lens 6 using the beam shaping mask 10 shown in FIG. 10.In FIG. 9, the ion beam 3 is assumed to have a positive electric charge.The quadrupole lens 6 can be an electrostatic lens instead of anelectromagnetic lens shown in FIG. 9.

FIGS. 10A to 10C are drawings that depict examples of the beam shapingmask 10 included in the ion implantation apparatus 1 shown in FIG. 1. InFIGS. 10A to 10C, the directions of the X, Y, and Z axes are the same. Alarge-diameter slit 21 and a small-diameter slit 22 are provided in thebeam shaping mask 10 shown in FIG. 10A. Because the beam shaping mask 10is provided downstream of the scanner 8 (closer to the substrate 11 thanthe scanner 8), an opening portion provided in the beam shaping mask 10has a slit shape that extends in a scanning direction of the ion beam 3as shown in FIG. 10A.

In the example of FIG. 10A, an arrangement is made such that the ionbeam 3 passes through the large diameter slit 21 when the first ionimplantation process is performed, and through the small-diameter slit22 when the second ion implantation process is performed. For example,the beam shaping mask 10 is connected to a shaft 24. The shaft 24 ismovably supported by a driving device 23 in the Y direction. With thismechanism, a position of the beam shaping mask 10 is adjusted accordingto the type of the ion implantation process.

FIG. 10B is a drawing that depicts an example of the beam shaping mask10 that includes a single slit 29. When performing the first ionimplantation process, the beam shaping mask 10 is moved to a position atwhich the ion beam 3 is not irradiated. In this example, the beamshaping mask 10 is removed from a path of the ion beam 3 in a directionopposite to the Y direction by a driving device (not shown).Furthermore, when performing the second ion implantation process, theposition of the beam shaping mask 10 is adjusted such that the ion beam3 passes through the slit 29.

FIG. 10C is a drawing that depicts an example of the beam shaping mask10 that has two holes. For example, the beam shaping mask 10 is arrangedupstream of the scanner 8 shown in FIG. 1 (closer to the ion source 2than the scanner 8), and the ion beam 3 is shaped before scanning.Switching between the two holes is performed similar to the exampleshown in FIG. 10A, that is, a large diameter hole 25 is used during thefirst ion implantation process and a small-diameter hole 26 is usedduring the second ion implantation process. Furthermore, when a singlehole is used, a process similar to the example of the single slit 29shown in FIG. 10B can be performed. The beam shaping mask 10 can be usedin combination with the quadrupole lens 6 shown in FIG. 9. The beamshaping mask 10 can be used in combination with optical elements thatare different from the quadrupole lens 6 included in the ionimplantation apparatus 1. Furthermore, the beam shaping mask 10 can beused independently to adjust the cross-sectional size of the ion beam 3.

Other Modifications

In the embodiments described above, a method is described in which thecross-sectional size of the ion beam 3 is adjusted using theacceleration tube 5, the quadrupole lens 6, or the beam shaping mask 10;however, other methods can also be used. For example, thecross-sectional size of the ion beam 3 that is irradiated on thesubstrate 11 can be adjusted by adjusting various parameters of the ionsource 2 (voltage applied on extracting electrodes, position, tilt ofthe extracting electrode, etc.).

In the embodiments described above, the ion implantation apparatus ofthe hybrid scanning system is described; however, the present inventionis also applicable to other types of ion implantation apparatuses. Forexample, the present invention can be applied to an ion implantationapparatus of a raster scanning system in which the substrate 11 is fixedand an ion beam is scanned in two orthogonal directions. In this case,to form the nonuniform dose amount distribution within the substrate 11,the ion implantation apparatus can be configured such that the scanningspeed of the ion beam in the two directions can be suitably adjustedaccording to the position on the substrate 11. Moreover, the first andsecond ion implantation processes that use different cross-sectionalsizes of the ion beams as described in the above embodiments can beperformed. Furthermore, a raster scanning system can be adopted in whichinstead of the substrate the ion beam is fixed, and the substrate isdriven in two orthogonal directions.

An implantation mechanism having a batch system where a plurality ofsubstrates is processed at one time can be adopted instead of animplantation mechanism having a single wafer system where the substratesare processed one by one. In this case, in the flowcharts shown in FIGS.2, 4, and 5, a plurality of the substrates is processed together insteadof one by one.

Alternatively, two ion implantation apparatuses can be used and thesubstrate can be continuously processed by an in-line system. Forexample, one ion implantation apparatus can be operated based on theoperating parameters corresponding to the first ion implantation processand the other ion implantation apparatus can be operated based on theoperating parameters corresponding to the second ion implantationprocess. Moreover, an arrangement can be made in which processingchambers of both the ion implantation apparatuses are connected and bysuccessively transporting the substrates between the different ionimplantation apparatuses without breaking vacuum, the substrates aresequentially processed.

The ion implantation apparatus of a system is described that scans thespot-like ion beam emitted from the ion source. However, the presentinvention can be applied to an ion implantation apparatus of a system inwhich a ribbon-like (substantially oblong shaped) ion beam is emittedfrom the ion source, expanded so as to be larger than the size of thesubstrate in a single plane, and irradiated on the substrate. Thepresent invention can be applied to an ion implantation apparatus of asystem in which a large ion source is prepared and a ribbon-like ionbeam larger than the size of the substrate is generated in the singleplane from the beginning instead of expanding the ion beam during theprocess.

In case of such ion implantation apparatuses, ion implantation isperformed within the entire substrate along a direction that issubstantially orthogonal to a spreading direction of the ion beam, thatis, along a short-side direction of the ion beam that has substantiallyan oblong shape, by driving the substrate. In these ion implantationapparatuses, the driving speed of the substrate can be changed to formthe non-uniform dose amount distribution within the substrate.

The cross-sectional shape of the ion beam that is irradiated on thesubstrate is almost rectangular. Therefore, the cross-sectional size ofthe ion beam that is irradiated on the substrate can be adjusted by thefirst and second ion implantation processes using the acceleration tubeand the quadrupole lens, and the beam shaping mask described in theabove embodiment, by controlling a width of the ribbon-like ion beamthat is irradiated on the substrate in the short-side direction.

The ion implantation process can be performed in an order given below.The first ion implantation process is temporarily stopped before it endscompletely and the ion implantation process is switched to the secondion implantation process. After the second ion implantation process iscompleted, the first ion implantation process is resumed.

Current density of the ion beam may be changed between the first ionimplantation process and the second ion implantation process. In thiscase, current density of the ion beam in the first implantation processmay be larger than current density of the ion beam in the second ionimplantation process.

Apart from the modifications described above, various modifications maybe made without departing from the spirit or scope of the generalinventive concept as defined by the appended claims and theirequivalents.

What is claimed is:
 1. A method of implanting ions into a substratewhile changing a relative positional relation between an ion beam andthe substrate, wherein a first ion implantation process in which auniform dose amount distribution is formed within the substrate and asecond ion implantation process in which a non-uniform dose amountdistribution is formed within the substrate are performed in apredetermined order, and a cross-sectional size of an ion beam that isirradiated on the substrate during the second ion implantation processis set smaller than a cross-sectional size of an ion beam that isirradiated on the substrate during the first ion implantation process.2. The method of implanting the ions according to claim 1, wherein, whenprocessing a plurality of substrates using the first and second ionimplantation processes, one of the ion implantation processes issuccessively performed on the substrates, and thereafter, the other ionimplantation process is successively performed on the substrates.